Updated: September 1, 2009
Applies To: Data Protection Manager, System Center Data Protection Manager 2007
A complete installation of System Center Data Protection Manager (DPM) 2007 includes the DPM server operating system, the DPM prerequisite software, and the DPM application. Each computer that DPM protects must meet the protected computer software requirements.
http://technet.microsoft.com/en-us/library/bb808755.aspx resolves the WMI service not found Error 820. Basically IIS doesn't have all the required components installed for DPM. Remove IIS and re-run DPM setup.